1. Field of the Invention
This invention relates generally to emulating the operation of phone extensions for analog and digital communication in a packet telephony distribution system.
2. Description of the Background Art
Typical telephone (phone) wiring in a home or business supports the use of one or two independent phone lines. Some premises support more phone lines. To provide access to phone lines, typically, several phone line jacks are connected to phone lines throughout the home. Sometimes, each phone line jack may be connected to all of the available phone lines, which permits the use of multi-line phones. Alternatively, each phone line jack may be connected to only one phone line.
When a home has an insufficient number of phone lines, a homeowner can order additional phone lines from a service provider. If the in-home wiring to support the new phone lines is already wired to the appropriate room or rooms, then there is no required change to the in-home wiring to support the new phone lines. However, if there are more desired phone lines than the existing in-home wiring can support, or if a phone jack is not connected to the desired phone line, then changes must be made to the in-home wiring. Such in-home wiring changes, particularly those that involve running new wires through the walls of a home, typically require a skilled phone technician at a relatively significant expense to the homeowner. The expense associated with providing new in-home wiring must be reduced to make the addition of new phone lines economical.
While it is currently uncommon for a household to have more phone lines than can be supported by existing in-home wiring, recent technological advances permit service providers, such as phone companies, cable TV companies, and other competing organizations, to offer additional phone lines at a relatively low cost. These technological advances permit these companies to make use of existing in-home wires to carry more than one phone signal at a time and are commonly called xe2x80x9cderivedxe2x80x9d phone lines. Derived phone lines make it significantly easier and less expensive to provide additional phone service.
One approach to avoid running new inside wiring when the number of phone lines required exceeds the capacity of the existing wiring and permitting a single in-home copper wire-pair to support more than one phone line, is via data networking technology. Packet data networks, such as Ethernet, are commonly used to share high-speed data information around a home. Packet data networks permit multiple devices to send and receive data on the same physical network by dividing data into discrete packets, and providing a means for the devices to negotiate which device may send data at a given time. While Ethernet networks require special wiring that few homes have installed, such as Cat5 (Category 5) copper cable, recent technological advances permit high-speed packet data networks to operate on existing in-home wires. Alternatively, a wireless high-speed packet data network obviates the need for in-home wiring.
An example of a new technology is phoneline networking, which permits packet data networking over a single wire-pair of existing in-home wiring. An industry standard for phone line networking is HomePNA (Home Phoneline Networking Alliance). HomePNA ensures that signals sharing a phone line with the POTS (Plain Old Telephone Service) line coexist and maximize throughput despite signaling constraints, such as attenuation and noise.
Another technology is powerline networking, which permits packet data networking over AC power lines in the home. An industry standard for powerline networking is HomePlug (HomePlug Powerline Alliance). HomePlug permits power outlets to provide a power source and also provide network ports for packet data networking. Since multiple power outlets are more common in a home than multiple phone line jacks, there is typically no need to install new in-home wiring.
Finally, wireless networking technology permits packet data networking with no wires at all and operates over distances that span the full length and breadth of most homes. Industry standards for wireless networking include IEEE 802.11 and HomeRF (Home Radio Frequency).
Technology also exists to permit a packet data network to carry phone signals. Such technologies include packet telephony protocols for transmitting and receiving digitized voice signals in addition to call-control signaling. One technology is Voice Over IP (Internet Protocol) or VoIP. A number of industry standards exist for VoIP, including ITU-T H.323, ITU-T H.248 (Megaco; Media Gateway Control Protocol), MGCP (Media Gateway Control Protocol), and SIP (Session Initiation Protocol). Other technologies exist for packet data transmission of phone signals that do not make use of the Internet Protocol, but make direct use of the underlying packet data networking mechanism.
By using packet telephony in conjunction with any of the networking technologies that operate wirelessly or use existing in-home wiring, it is possible to distribute many phone lines throughout the home without installing new wires, avoiding the associated labor and cost. While all of the phones are connected to the same physical network, each phone can virtually connect to a separate phone line.
A problem occurs when one or more derived phone lines are available through a gateway in a packet data network, but users do not view the derived phone lines as a substitute for analog phone lines. For example, some derived phone lines, such as VoIP lines, are available that provide very low cost long-distance or international calling, but do not provide the quality of an analog phone line. Thus, it is desirable that the user using a phone should be able to make and accept calls on either the analog phone lines or the VoIP lines. For outgoing calls, the user may wish to decide whether to use the analog phone lines or VoIP lines depending on the destination of the call. Alternatively, the user can consider other factors such as cost and line utilization.
Typically, when multiple phones in different parts of the home are connected to the same analog phone line, the phones behave as extensions on the analog phone line. For example, when one of the phones connected to the analog phone line is in use, the user picking up the handset of another phone on the same analog phone line would not hear the dial tone, but instead would immediately join the call already in progress. When one of the phones on the analog phone line is in use and the phone is off hook, it is useful for the user about to use another phone on the same analog phone line to know that the line is in use. Many phones include line-in-use indicators on a second or subsequent phone to inform the user that a call is in progress or that the analog phone line is available. Multi-line phones often have such line-in-use indicators to inform the user which analog phone line is not in use.
Line-in-use indicators operate by detecting a loop voltage from the connected analog phone line. When all phones connected to the analog phone line are not in use, there is little or no current flowing on the analog phone line, and the loop voltage is high. When one or more phones are off hook, the off hook phones draw current from the analog phone line, resulting in a voltage drop. Other phones connected to the same analog phone line can detect the voltage drop. Further, the presence or absence of the voltage drop permits other phones to determine whether or not the analog phone line is in use.
The characteristics associated with phone extension operation and line-in-use indicators are an important part of the typical use of phones in the home or business. Therefore, to provide the virtual equivalent of in-home phone wiring in the packet telephony distribution system, it is important to emulate these characteristics. Existing packet telephony protocols such as VoIP protocols, do not include the ability to specifically emulate these characteristics of in-home phone usage. Therefore, what is needed is a technique that permits a phone system to emulate the behavior of a typical in-home phone while connected to a packet telephony distribution system.
A system for emulating phone extensions in a packet telephony distribution system comprises a gateway coupled to a telephone network, the gateway configured to dynamically control communication between a plurality of communication devices and to a plurality of data network and analog lines in the telephone network, wherein the gateway is further configured to transmit dial tones and line-in-use indicators to the plurality of communication devices, and a plurality of adapters coupled to the plurality of communication devices, the plurality of adapters being configured to receive incoming calls via the plurality of data network and analog lines and to selectively make outgoing calls via the plurality of data network and analog lines.
A system also includes a method for emulating phone extensions in a packet telephony distribution system, comprising the steps of configuring a gateway to identify a plurality of communication devices, receiving an incoming call signal from a data network and analog line at the gateway, transmitting a dial tone to the plurality of communication devices using the gateway, and transmitting a line-in-use indicator to the plurality of communication devices using the gateway.